<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var x;
        let y;
        const PI=3.14;
        console.log(x,y,PI);
        let name='如花';
        console.log(name);

        let age=19;
        if (age>18) {
            console.log('成年了');
        } else {
            console.log('未成年');
        }

        console.log('FOR循环');
        for (let index = 0; index < 10; index++) {
            console.log(index);
        }
    </script>
</body>
</html>